1. Field of the Invention
The present invention relates to a chemically stabilized herbicidal oil-based suspension containing N-[(4,6-dimethoxypyrimidin-2-yl)aminocarbonyl]-3-dimethylaminocarbonyl-2-p yridinesulfonamide (hereinafter referred to as compound A) and/or its salt as an effective herbicidal component, which suppress the decomposition of compound A and/or its salt.
2. Description of the Related Art
The present inventors found previously that pyridinesulfonamide series compounds including compound A and the salts thereof exhibit a very high herbicidal effect when they can be applied to a wide range of weeds including strongly harmful weeds, and filed European Patent Application No. 87300502.9 (or Laid-open European Patent Application No. 232067) on the basis of this finding. The inventors also found that a suspended composition comprising at least one compound selected from the pyridinesulfonamide series compounds and the salts thereof, a vegetable oil and a surfactant, which are mixed at a predetermined ratio, permits improving the herbicidal effect and decreasing the amount of the effective herbicidal component, and filed European Patent Application No. 88309772.7 (or Laid-open European Patent Application No. 313317).
On the other hand, various methods have been proposed to date for suppressing the decomposition of herbicidal sulfonylurea series compounds similar to compound A within preparations of agricultural chemicals so as to stabilize the formulations. For example, a stabilized aqueous composition containing a carboxylate or an inorganic salt is disclosed in Published Unexamined Japanese Patent Application No. 59-205305 (or Laid-open European Patent Application No. 124295). A stabilized granular composition containing calcium carbonate and, as required, sodium tripolyphosphate is disclosed in Published Unexamined Japanese Patent Application No. 62-84004. A stabilized solid formulations of agricultural chemicals containing a mineral-based carrier and a vegetable oil or a solvent having a high boiling point is disclosed in Published Unexamined Japanese Patent Application No. 63-23806. Further, various stabilized compositions of agricultural chemicals containing urea, thiourea or derivatives thereof are disclosed in Published Unexamined Japanese Patent Application No. 50-40739, Published Unexamined Japanese Patent Application No. 51-7128, Published Unexamined Japanese Patent Application No. 51-12930, Published Unexamined Japanese Patent Application No. 52-117422, Published Unexamined Japanese Patent Application No. 56-169606 (or Laid-open Belgian Patent Application No. 888634 or Laid-open British Patent Application No. 2074871), and Published Unexamined Japanese Patent Application No. 57-18605.
However, any of the publications exemplified above does not teach at all an idea of adding urea to a herbicidal oil-based suspension containing compound A and/or a salt thereof for chemically stabilizing it.